The foundry industry is an important component of the economy on which other progressive industries depend. The reliability of the products it manufactures is determined by the technologies used, but, most importantly, it ensures the expected level of quality. The purpose of the article is to develop a synergistic quality-cost model for the improvement of casting products. The model is based on an integral methodological configuration that makes it possible to determine the level of relevance of the causes of casting nonconformity in the quality-cost context. The model integrates techniques such as the Pareto-Lorenz diagram, ranking, brainwriting, Ishikawa diagram, Likert rating scale, and matrix diagram. Verification of the method by its implication in the manufacturing process of a gearbox casting is performed. The model makes it possible to identify quality-cost relationships between key categories of problem causes and major product nonconformities. The main causes of the loss of quality stability of the analyzed product are found to be low quality of molding sand, poor technical condition of foundry equipment (too infrequent repairs and overhauls), and ineffective quality control. Carrying out the analysis made it possible to develop appropriate improvement measures. It is proposed to implement changes in the casting process, implement the TPM method, conduct periodic training, develop job instructions, implement a control system, and provide supervision of employees. Further research directions will concern the implications of the method within the other positions in the casting company and its development towards automation of analysis.